The chemical interaction of phosphorofluoridate (PO3F2-) with amorphous calcium phosphate (ACP) and crystalline apatite (CA) is being studied. The extent of PO3F2- adsorption on ACP and CA, the stability of adsorbed PO3F2-, and the inhibition of adsorption by other anionic species are being investigated. PO3F2- reactivity will be correlated with the composition, texture and prior chemical history of ACP and CA.